用戶評論:

[#1]

florenxe [2015-10-07 18:53:45]

//a?nice?little?way?to?print?leap?years?using?array

for?($leap?=?2032;?$leap?

{

$arr?=?[];

array_push($arr,?$leap);

foreach($arr?as?$a)?{

echo?($a).PHP_EOL;

}

}

[#2]

aditycse at gmail dot com [2015-08-10 09:23:11]

//Array?can?have?following?data?type?in?key?i.e?string,integer

//Behaviour?of?array?in?case?of?array?key?has?data?type?float?or?double

$exampleArray?=?array(0,

1,

"2.99999999"?=>?56,

2?=>?2,

3.9999?=>?3,

3?=>?3.1,

true?=>?4,

false?=>?6,

);

//array?structure

print_r($exampleArray);

//array?of?array?keys

print_r(array_keys($exampleArray));

[#3]

perske at uni-muenster dot de [2015-04-18 23:16:20]

Regarding?this?note:????Strings?containing?valid?integers?will?be?cast?to?the?integer?type.??

This?is?true?only?for?decimal?integers?without?leading???+??,?but?not?for?octal,?hexadecimal,?or?binary?integers.

Example:

$array=?array("0"=>"a","-1"=>"b","+1"=>"c","00"=>"d","01"=>"e","0x1"=>"f",

);var_dump($array);?>

This?example?will?output:

array(7)?{

[0]=>

string(1)?"a"

[-1]=>

string(1)?"b"

["+1"]=>

string(1)?"c"

["00"]=>

string(1)?"d"

["01"]=>

string(1)?"e"

["0x1"]=>

string(1)?"f"

}

Thus?different?strings?are?always?mapped?to?different?array?keys.

[#4]

mathiasgrimm at gmail dot com [2014-09-29 16:20:22]

$a['a']?=null;$a['b']?=?array();

echo$a['a']['non-existent'];//?DOES?NOT?throw?an?E_NOTICE?error?as?expected.echo$a['b']['non-existent'];//?throws?an?E_NOTICE?as?expected?>

I?added?this?bug?to?bugs.php.net?(https://bugs.php.net/bug.php?id=68110)

however?I?made?tests?with?php4,?5.4?and?5.5?versions?and?all?behave?the?same?way.

This,?in?my?point?of?view,?should?be?cast?to?an?array?type?and?throw?the?same?error.

This?is,?according?to?the?documentation?on?this?page,?wrong.

From?doc:

"Note:

Attempting?to?access?an?array?key?which?has?not?been?defined?is?the?same?as?accessing?any?other?undefined?variable:?an?E_NOTICE-level?error?message?will?be?issued,?and?the?result?will?be?NULL."

[#5]

brta dot akos at gmail dot com [2014-01-10 13:45:43]

Why?not?to?user?one-based?arrays:

$a=?array(1=>'a','b','d');print_r($a);array_splice($a,2,0,'c');print_r($a);?>

output:

Array?(?[1]?=>?a?[2]?=>?b?[3]?=>?d?)?Array?(?[0]?=>?a?[1]?=>?b?[2]?=>?c?[3]?=>?d?)

[#6]

note dot php dot lorriman at spamgourmet dot org [2014-01-09 15:01:55]

There?is?another?kind?of?array?(php>=??5.3.0)?produced?by

$array?=?new?SplFixedArray(5);

Standard?arrays,?as?documented?here,?are?marvellously?flexible?and,?due?to?the?underlying?hashtable,?extremely?fast?for?certain?kinds?of?lookup?operation.

Supposing?a?large?string-keyed?array

$arr=['string1'=>$data1,?'string2'=>$data2?etc....]

when?getting?the?keyed?data?with

$data=$arr['string1'];

php?does?*not*?have?to?search?through?the?array?comparing?each?key?string?to?the?given?key?('string1')?one?by?one,?which?could?take?a?long?time?with?a?large?array.?Instead?the?hashtable?means?that?php?takes?the?given?key?string?and?computes?from?it?the?memory?location?of?the?keyed?data,?and?then?instantly?retrieves?the?data.?Marvellous!?And?so?quick.?And?no?need?to?know?anything?about?hashtables?as?it's?all?hidden?away.

However,?there?is?a?lot?of?overhead?in?that.?It?uses?lots?of?memory,?as?hashtables?tend?to?(also?nearly?doubling?on?a?64bit?server),?and?should?be?significantly?slower?for?integer?keyed?arrays?than?old-fashioned?(non-hashtable)?integer-keyed?arrays.?For?that?see?more?on?SplFixedArray?:

http://uk3.php.net/SplFixedArray

Unlike?a?standard?php?(hashtabled)?array,?if?you?lookup?by?integer?then?the?integer?itself?denotes?the?memory?location?of?the?data,?no?hashtable?computation?on?the?integer?key?needed.?This?is?much?quicker.?It's?also?quicker?to?build?the?array?compared?to?the?complex?operations?needed?for?hashtables.?And?it?uses?a?lot?less?memory?as?there?is?no?hashtable?data?structure.?This?is?really?an?optimisation?decision,?but?in?some?cases?of?large?integer?keyed?arrays?it?may?significantly?reduce?server?memory?and?increase?performance?(including?the?avoiding?of?expensive?memory?deallocation?of?hashtable?arrays?at?the?exiting?of?the?script).

[#7]

ivegner at yandex dot ru [2013-08-28 08:43:28]

Note?that?objects?of?classes?extending?ArrayObject?SPL?class?are?treated?as?arrays,?and?not?as?objects?when?converting?to?array.

private$private='private';

public$hello='world';

}$object=?newArrayObjectExtended();$array=?(array)$object;//?This?will?not?expose?$private?and?$hello?properties?of?$object,

//?but?return?an?empty?array?instead.var_export($array);?>

[#8]

chris at ocportal dot com [2013-05-28 09:01:11]

Note?that?array?value?buckets?are?reference-safe,?even?through?serialization.

$x='initial';$test=array('A'=>&$x,'B'=>&$x);$test=unserialize(serialize($test));$test['A']='changed';

echo$test['B'];//?Outputs?"changed"?>

This?can?be?useful?in?some?cases,?for?example?saving?RAM?within?complex?structures.

[#9]

gtisza at gmail dot com [2013-02-12 14:17:26]

Be?very?careful?when?using?a?result?as?an?array.?<?phpecho $a['foo']['bar']['baz']?>?will?throw?an?error?if?$a?is?an?object,?and?throw?a?warning?if?$a?is?an?array?but?does?not?have?the?right?keys,?but?it?will?silently?return?true?if?$a?is?null?or?boolean?or?int,?and?if?$a?is?a?string,?it?will?return?its?first?character.?(This?is?true?even?with?E_STRICT?set.)?This?can?be?a?major?gotcha?with?functions?which?return?null?or?false?if?they?are?unsuccessful.

[#10]

martijntje at martijnotto dot nl [2012-03-29 07:48:35]

Please?note?that?adding?the?magic?__toString()?method?to?your?objects?will?not?allow?you?to?seek?an?array?with?it,?it?still?throws?an?Illegal?Offset?warning.

The?solution?is?to?cast?it?to?a?string?first,?like?this

$array[(string)?$stringableObject]

[#11]

mlvljr [2011-05-20 06:37:27]

please?note?that?when?arrays?are?copied,?the?"reference?status"?of?their?members?is?preserved?(http://www.php.net/manual/en/language.references.whatdo.php).

[#12]

Walter Tross [2010-08-12 11:04:39]

It?is?true?that?"array?assignment?always?involves?value?copying",?but?the?copy?is?a?"lazy?copy".?This?means?that?the?data?of?the?two?variables?occupy?the?same?memory?as?long?as?no?array?element?changes.

E.g.,?if?you?have?to?pass?an?array?to?a?function?that?only?needs?to?read?it,?there?is?no?advantage?at?all?in?passing?it?by?reference.

[#13]

ken underscore yap atsign email dot com [2008-01-09 08:00:16]

"If?you?convert?a?NULL?value?to?an?array,?you?get?an?empty?array."

This?turns?out?to?be?a?useful?property.?Say?you?have?a?search?function?that?returns?an?array?of?values?on?success?or?NULL?if?nothing?found.

Now?you?want?to?merge?the?array?with?another?array.?What?do?we?do?if?$values?is?NULL??No?problem:

Voila.

[#14]

carl at linkleaf dot com [2007-09-06 11:36:40]

Its?worth?noting?that?there?does?not?appear?to?be?any?functional?limitations?on?the?length?or?content?of?string?indexes.?The?string?indexes?for?your?arrays?can?contain?any?characters,?including?new?line?characters,?and?can?be?of?any?length:

$key="XXXXX";$test=?array($key=>"test5");

for?($x=0;$x<500;$x++)?{$key.="X";$value="test".strlen($key);$test[$key]?=$value;

}

echo"

";print_r($test);

echo"

";?>

Keep?in?mind?that?using?extremely?long?array?indexes?is?not?a?good?practice?and?could?cost?you?lots?of?extra?CPU?time.?However,?if?you?have?to?use?a?long?string?as?an?array?index?you?won't?have?to?worry?about?the?length?or?content.

[#15]

Spudley [2007-03-16 01:44:27]

On?array?recursion...

Given?the?following?code:

$myarray=?array('test',123);$myarray[]?=?&$myarray;print_r($myarray);?>

The?print_r()?will?display?*RECURSION*?when?it?gets?to?the?third?element?of?the?array.

There?doesn't?appear?to?be?any?other?way?to?scan?an?array?for?recursive?references,?so?if?you?need?to?check?for?them,?you'll?have?to?use?print_r()?with?its?second?parameter?to?capture?the?output?and?look?for?the?word?*RECURSION*.

It's?not?an?elegant?solution,?but?it's?the?only?one?I've?found,?so?I?hope?it?helps?someone.

[#16]

[2006-10-25 09:18:13]

This?page?should?include?details?about?how?associative?arrays?are?implemened?inside?PHP;?e.g.?using?hash-maps?or?b-trees.

This?has?important?implictions?on?the?permance?characteristics?of?associative?arrays?and?how?they?should?be?used;?e.g.?b-tree?are?slow?to?insert?but?handle?collisions?better?than?hashmaps.??Hashmaps?are?faster?if?there?are?no?collisions,?but?are?slower?to?retrieve?when?there?are?collisions.??These?factors?have?implictions?on?how?associative?arrays?should?be?used.

[#17]

ia [AT] zoznam [DOT] sk [2005-09-30 02:55:37]

Regarding?the?previous?comment,?beware?of?the?fact?that?reference?to?the?last?value?of?the?array?remains?stored?in?$value?after?the?foreach:

<?phpforeach ?($arras$key=>?&$value)

{$value=1;

}//?without?next?line?you?can?get?bad?results...

//unset(?$value?);$value=159;?>

Now?the?last?element?of?$arr?has?the?value?of?'159'.?If?we?remove?the?comment?in?the?unset()?line,?everything?works?as?expected?($arr?has?all?values?of?'1').

Bad?results?can?also?appear?in?nested?foreach?loops?(the?same?reason?as?above).

So?either?unset?$value?after?each?foreach?or?better?use?the?longer?form:

<?phpforeach ?($arras$key=>$value)

{$arr[$key]?=1;

}?>

[#18]

caifara aaaat im dooaat be [2005-08-28 02:28:08]

[Editor's?note:?You?can?achieve?what?you're?looking?for?by?referencing?$single,?rather?than?copying?it?by?value?in?your?foreach?statement.?See?http://php.net/foreach?for?more?details.]

Don't?know?if?this?is?known?or?not,?but?it?did?eat?some?of?my?time?and?maybe?it?won't?eat?your?time?now...

I?tried?to?add?something?to?a?multidimensional?array,?but?that?didn't?work?at?first,?look?at?the?code?below?to?see?what?I?mean:

$a1=?array("a"=>0,"b"=>1);$a2=?array("aa"=>00,"bb"=>11);$together=?array($a1,$a2);

foreach($togetheras$single)?{$single["c"]?=3;

}print_r($together);foreach($togetheras$key=>$value)?{$together[$key]["c"]?=3;

}print_r($together);?>

[#19]

jeff splat codedread splot com [2005-04-21 09:16:32]

Beware?that?if?you're?using?strings?as?indices?in?the?$_POST?array,?that?periods?are?transformed?into?underscores:

printf("POST:?");print_r($_POST);printf("
");?>

">

Once?you?click?on?the?button,?the?page?displays?the?following:

POST:?Array?(?[Windows3_1]?=>?Sux?)

[#20]

lars-phpcomments at ukmix dot net [2005-03-28 08:40:25]

Used?to?creating?arrays?like?this?in?Perl?

@array?=?("All",?"A".."Z");

Looks?like?we?need?the?range()?function?in?PHP:

$array=array_merge(array('All'),range('A','Z'));?>

You?don't?need?to?array_merge?if?it's?just?one?range:

$array=range('A','Z');?>

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